The natural history of low-risk non-muscle-invasive bladder cancer: a collaborative multi-centre study

Background: International guidelines vary in terms of their definition and recommendation for management of low-risk non-muscle-invasive bladder cancer (LRNMIBC). The ideal management for this large subset of bladder cancer patient remains unclear.

Objective: To evaluate long-term outcomes of patients with LRNMIBC. As a secondary objective, to assess for intergroup heterogeneity in disease-specific outcomes between G1 and G2LG diseases.

Methods: A multi-centre, retrospective study of patients who met the 2015 NICE definition of LRNMIBC. Timeline of diagnosis ranged from 01/01/2012 to 30/06/2016.

Results: A total 390 patients had available follow-up data (G1: 142, G2LG: 249). Over a median follow-up time of 36 months (IQR 25-50), 29.2% of the patients developed a recurrence. G2LG patients were statistically more likely to develop a recurrence (G1: 26.8%, G2LG: 33.7%, p < 0.05). 51.8% of recurrences occurred after 1 year of surveillance. Progression to high-grade disease occurred in 1.8% (n = 7, G1: 3, G2LG: 4) and a further 1.0% (n = 4, G1:3, G2LG: 1) of patients developed muscle-invasive bladder cancer (MIBC).

Conclusion: The majority of recurrences occurred after 1 year of surveillance. The risk of disease progression was low; however, this was observed in a cohort of patients with regular cystoscopic follow-up. The risk may be higher if patients were pre-maturely discharged. If a 5-year surveillance programme were to be followed, 96.5% of recurrences would be captured. Lastly, there appears to be intergroup heterogeneity within LRNMIBC with G2LG patients having a statistically higher risk of recurrence compared to G1.